At the point of care, three-dimensional medical image data composed of a plurality of cross-sectional images (or slice images) are captured by using medical image capturing apparatuses such as an X-ray CT apparatus, an MRI apparatus and a PET apparatus. When a doctor performs image diagnosis by interpreting the medical image data, it is often the case that a plurality of cross-sectional images are displayed by being sequentially switched. As a result of the cross-sectional images being displayed by being sequentially switched, the doctor can observe the entirety of the three-dimensional medical image data, and find an abnormal shadow that appears in some of the cross-sectional images.
With a recent trend toward an increase in the number of patients due to the aging of population and an increase in the sophistication of medical image capturing apparatuses, the number of tests that require interpretation, the type of medical images taken for a single test, the number of cross-sectional images included in one set of medical images, and image resolution are also increasing. For this reason, a doctor is required to read a large number of cross-sectional images in a limited amount of time, and thus the burden on doctors to interpret medical images is rapidly increasing. As a result, the possibility that a doctor may miss an abnormal shadow in some of the images interpreted (the occurrence of an oversight in interpretation) is increasing more than ever. The occurrence of an oversight in interpretation increases the risk that a doctor may miss an abnormal shadow, leading to a disadvantage for the patients.
Japanese Patent Laid-Open No. 2007-319327 discloses a technique for recording sight-line information of a reader and GUI operations in a time series during interpretation of medical images. With this technique, the system measures and records the sight-line of the reader reading images that need to be interpreted, and thus the reader can identify observed areas observed by the reader and unobserved areas, as a result of which it is possible to indicate an interpretation oversight in the unobserved areas.
The conventional technique described above, however, sets a predetermined range including the center coordinates of the sight-line as focus vision and sets areas in the image where the focus vision has scanned as observed areas, and thus does not give consideration to the fact that the focus vision of the reader changes according to how the reader observes. To be specific, in the case where a doctor is thoroughly observing one cross-sectional image, he/she is gazing at a relatively narrow area, whereas in the case where the doctor is observing a plurality of cross-sectional images for the presence or absence of an abnormal shadow by sequentially switching and displaying the images, he/she is viewing a wider range because of dynamic visual stimulation. Accordingly, with the conventional technique, the reader may not always correctly identify observed areas observed by the reader. In this case, a problem occurs in that an interpretation oversight may be indicated in the observed areas. Or conversely, a problem occurs in that an interpretation oversight may not be indicated in unobserved areas. If such an erroneous indication of interpretation oversight occurs, the reader cannot smoothly perform interpretation of medical images. Accordingly, in order to assist interpretation of medical images, it is an important issue to allow the reader to always appropriately identify observed areas.